Major problems are related to oxide film existent on aluminum wire surfaces, which are difficult to break and to establish a good electrical connection and the galvanic corrosion process while both aluminum and copper conductors are in contact.
Electrical power distribution systems frequently include a mixture of aluminum and copper conductors at various portions of the distribution system. When used in contact with one another, aluminum and copper conductors, a corrosion process erodes the aluminum cable. This corrosion is typically caused where the copper and aluminum interface is exposed to the outdoor environment, or to other corrosive environment.
Copper cables have greater current capacity and are easier to connect, since its oxide layer surface is easily broken. Aluminum cables are lighter and cheaper, while its current capacity is about just 60% of the equivalent copper cable size. Typical power networks are assembled using aluminum cables for low voltage distribution and copper cables to feed residential and commercial customers. Copper cables are commonly used for residential and commercial customers since the metering equipment electrical contacts are normally made from copper alloys. In order to avoid corrosion problems with the power meter connectors, copper cables are preferred, notwithstanding its higher cost.
Conversely, aluminum conductors have an undesirable characteristic of forming a high resistance film of aluminum oxide on the outside of the conductor when it is exposed to the air. Aluminum oxide is a fast forming, hard, non-conductive coating that develops on the surface of aluminum conductors exposed to air. Unlike copper oxides, aluminum oxide is not visually obvious and should be assumed to exist in all cases of bare aluminum. To prevent high-resistance connections, which can be fire hazards, it is necessary to remove from a conductor's surface prior to making a connection. Wire brushing and the immediate application of an oxide inhibitor are recommended to prevent the reformation of the non-conductive coating prior to connector installation. An alternate method that is used to achieve low contact resistance is for the connection methodology to physically break through the aluminum oxide layer as the connection is being made. Even with these types of connections, however, cleaning the conductor is still recommended prior to installation.
The typical solution for oxidation is conductor preparation by cleaning its surface. However, after the oxide is cleaned, by scraping or wire-brushing the conductor, the oxidation reforms quickly. Unless the connection is properly prepared, a high resistance contact is the result and heating is likely to occur.
An oxidation inhibitor compound, e.g., grease, is frequently applied to the conductor after the connection is made, to provide an oxygen barrier for the connection, to avoid new oxide layer formation.
In addition, aluminum also suffers from other forms of corrosion, e.g., creep corrosion.
What is needed is a system and/or method that satisfies one or more of these needs or provides other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the claims, regardless of whether they accomplish one or more of the aforementioned needs.